roman numerals in go

main.go

package main

import (
	"flag"
	"fmt"
	"strings"
)

var (
	to    = flag.Int("to", 0, "convert int to roman")
	from  = flag.String("from", "", "convert roman to int")
	chars = [...]string{"M", "CM", "C", "XC", "L", "XL", "X", "IX", "V", "IV", "I"}
	vals  = [...]int{1000, 900, 100, 90, 50, 40, 10, 9, 5, 4, 1}
)

func fromRoman(in string) (out int) {
	for i, char := range chars {
		for strings.HasPrefix(in, char) {
			out += vals[i]
			in = strings.TrimPrefix(in, char)
		}
	}

	return
}

func toRoman(in int) (out string) {
	for i, val := range vals {
		for in >= val {
			in -= val
			out += chars[i]
		}
	}

	return
}

func main() {
	flag.Parse()

	if *from != "" {
		val := fromRoman(*from)
		fmt.Printf("FROM: %v, INT: %v", *from, val)
	}

	if *to > 0 {
		roman := toRoman(*to)
		fmt.Printf("TO: %v, ROMAN: %v", *to, roman)
	}
}